Performing a remote point-in-time copy to a source and target storages in further mirror copy relationships

ABSTRACT

Provided are a computer program product, system, and method for performing a remote point-in-time copy to a source and target storages in further mirror copy relationships. Each of a plurality of source copy relationships is from the source storage to one corresponding source copy storage. Each of a plurality of target copy relationships is from the target storage to one corresponding target copy storage, where in each relationship an indicator indicates whether to use a remote first type copy operation. The first type copy operation is used to copy data from the source storage to the target storage and copy data from the source copy storage to the target copy storage for the determined source and target copy relationships having the indicator set. A second type of copy operations is used for source and target relationships not having the indicator set.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a computer program product, system, andmethod for performing a remote point-in-time copy to a source and targetstorages in further mirror copy relationships.

2. Description of the Related Art

In a storage environment, a storage controller may create point-in-time(“PiT”) copies of a production volume using point-in-time copytechniques, such as the IBM FlashCopy® (FlashCopy is a registeredtrademark of IBM), snapshot, etc. A point-in-time copy replicates datain a manner that appears instantaneous and allows a host to continueaccessing the source and target volumes while actual data transfers tothe target volume are deferred to a later time. The point-in-time copyappears instantaneous because complete is returned to the copy operationin response to generating the relationship data structures withoutcopying the data from the source to the target volumes. Point-in-timecopy techniques typically defer the transfer of the data in the sourcevolume at the time the point-in-time copy relationship was establishedto the copy target volume until a write operation is requested to thatdata block on the source volume. Data transfers may also proceed as abackground copy process with minimal impact on system performance. Thepoint-in-time copy relationships that are immediately established inresponse to the point-in-time copy command include a bitmap or otherdata structure indicating the location of blocks in the volume at eitherthe source volume or the target volume. The point-in-time copy comprisesthe combination of the data in the source volume and the data to beoverwritten by the updates transferred to the target volume.

In a mirror copy relationship, a primary storage comprises the storageor volumes from which data is physically copied to a secondary storageor volume. To address a situation where a mirror primary volume on alocal site becomes the target of a PiT copy or FlashCopy operation froma source volume on the local site, which source volume may also be aprimary volume in a mirror copy, IBM developed the Remote Pair FlashCopyoperation so that when data is FlashCopied, i.e., PiT copied, from asource volume to a target volume on a local site when the source andtarget volumes are also primary volumes in mirror copy relationships tosecondary volumes at a remote site, an equivalent FlashCopy operation isperformed on the remote site to FlashCopy the remote secondary volumesin the mirror relationship so that the mirror copy to the secondaryvolumes can be accomplished instantly with a PiT copy.

This Remote Pair FlashCopy operation ensures that the mirror copyrelationship is not interrupted due to the primary storage in the mirrorrelationship becoming the target of a FlashCopy relationship. WithRemote Pair FlashCopy, when the FlashCopy source and target devices areboth mirror primary devices in full duplex state, the FlashCopy isperformed locally between the source and target, i.e., the primaryvolumes in the mirror relationship, and then the FlashCopy is sentinband to the FlashCopy server having the secondary volumes of themirror and performed remotely between the two secondary volumes.

By ensuring that the mirror relationships are not interrupted by theFlashCopy operation, the mirror storages remain available for a failoveroperation from the mirror secondary storage to the mirror primarystorage, such as the IBM HyperSwap®, which provides continuousavailability for disk failures by maintaining synchronous copies of allprimary disk volumes on one or more primary storage systems to one ormore target (or secondary) storage systems. (HyperSwap is a registeredtrademark of IBM in countries throughout the world).

SUMMARY

Provided are a computer program product, system, and method forperforming a remote point-in-time copy to a source and target storagesin further mirror copy relationships. A plurality of source copyrelationships are established, wherein each of the source copyrelationships is from the source storage to one corresponding sourcecopy storage, wherein data is copied from the source storage to thesource copy storages in the copy relationships to provide a mirror copyof data at the source storage at the source copy storages. A pluralityof target copy relationships are established, wherein each of the targetcopy relationships is from the target storage to one correspondingtarget copy storage, wherein data is copied from the target storage tothe source copy storages to provide a mirror copy at the source copystorages. For each of the source and target copy relationships, anindicator indicates whether to use a remote first type copy operation. Adetermination is made from the indicator the source and target copyrelationships indicating to use the remote first type of copy operation.The first type copy operation is used to copy data from the sourcestorage to the target storage. The first type of copy operations to copydata from the source copy storage to the target copy storage for thedetermined source and target copy relationships having the indicator setto use the remote first type copy operation in response to using thefirst type copy operation to copy data from the source storage to thetarget storage. A second type of copy operations is used to copy datafrom the source storage to the source copy storage and from the targetstorage to the target copy storage in the source and targetrelationships having the indicator set to not use the remote first typeof copy operation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of a storage replication environment.

FIG. 2 illustrates an embodiment of a copy relationship.

FIG. 3 illustrates an embodiment of a remote pair point-in-time (“PiT”)copy establish request.

FIG. 4 illustrates an embodiment of operations to establish mirror copyrelationships.

FIG. 5 illustrates an embodiment of operations to process a remote pairPiT copy establish request.

FIG. 6 illustrates a computing environment in which the components ofFIG. 1 may be implemented.

DETAILED DESCRIPTION

Described embodiments provide techniques for performing a remote PiTcopy operation in environments when the source and target storages ofthe remote PiT copy operation each comprise primary volumes in multiplemirror copy relationships having secondary volumes in a remote storage.With described embodiments, the copy relationship includes an indicatorindicating whether that copy relationship may be subject to a remote PiTcopy operation where the PiT copy operation is performed at a remotesite including the secondary storages of primary volumes that are sourceand target storages in a PiT copy relationship, so the mirror copy tothe secondary volumes whose primary volumes are source and targetstorages subject to the PiT copy can be performed by performing a PiTcopy of the secondary storages in the mirror relationship at the remotesite. The indicator may be used to determine whether there is ambiguityas to which copy relationships to use for the remote PiT copy operationand how to handle any determined ambiguity.

FIG. 1 illustrates an embodiment of a replication copy storageenvironment having a host system 100 that is connected to a plurality ofstorage servers 102 a, 102 b, 102 c. Storage server 102 a manages asource storage 104 a having one or more volumes and a target storage 104b having one or more volumes, where the data in the source storage 104 amay be copied to the target storage 104 b. The source storage 104 a maybe in separate mirror copy relationships 200 ₁ and 200 ₂ with sourcecopy storages 108 a and 108 b which are located in different storageservers 102 b and 102 c, respectively. Likewise, the target storage 104b may be in copy relationships 200 ₃ and 200 ₄ with target copy storages110 a and 110 b which are located in the different storage servers 102 band 102 c, respectively. In an alternative embodiment, the secondarycopy storages 108 a, 108 b, 110 a, 110 b may all be in one storageserver. The host 100 and storage servers 102 a, 102 b, 102 c maycommunicate over a network 112. There may be additional hosts (notshown) that provide Input/Output (I/O) requests to the source 104 a andtarget 104 b storages. The data in the source storage 104 a may becopied to the target storage 104 b in the manner described below.

The host system 100 includes a replication manager 114 to establishmirror copy relationships 200 between the different storages as shown bythe copy relationships 200 ₁, 200 ₂, 200 ₃, and 200 ₄. In each of thecopy relationships, data is synchronized or copied from a primarystorage to a secondary storage, as shown by the direction of the arrowsin the illustrated copy relationships 200 ₁, 200 ₂, 200 ₃, and 200 ₄.The host 100 further includes a failover manager 116 to use to implementa failover from a primary storage to a secondary storage in a copyrelationship 200.

Each of the storage servers 102 a, 102 b, 102 c may include, as shownwith respect to storage server 102 a, an I/O manager 120 to manage I/Orequests and a replication manager 122 to manage copy relationships 200a, such as copying data written to the source 104 a, and target 104 bstorages to any source 108 a, 108 b and target 110 a, 110 b copystorages to synchronize data therebetween.

In the embodiment of FIG. 1 there are three storage servers 102 a, 102b, 102 c and two mirror copy relationships for each of the source 104 aand target 104 b storages. However, in different implementations theremay be at least two secondary storage systems and more than threesecondary storage systems. Further, there may be more copy relationshipsfrom the source 104 a and target 104 b storages than shown by way ofexample.

The storage servers 102 a, 102 b, 102 c may comprise an enterprisestorage controller/server suitable for managing access to attachedstorage devices, such as, but not limited to, the International BusinessMachine Corporation's (“IBM”) DS8000® storage system or other vendorstorage servers known in the art. (DS8000 is a registered trademark ofIBM in countries throughout the world).

In one embodiment, the replication manager 114, 122 comprises a programfor managing the mirroring of volumes across systems, such as, but notlimited to, the IBM mirroring programs Geographically Dispersed ParallelSysplex® (GDPS)®, and Tivoli® Storage Productivity Center forReplication (TPC-R) that define a replication session and copy pairs200. Different types of techniques may be selected to copy the data,such as synchronous mirroring, asynchronous mirroring or point-in-timecopying, or combinations of multiple of these different mirroring types.The failover manager 116 may comprise a program suitable for handlingthe failover of one of the source copy storages 108 a, 108 b to thesource storage 104 a and a failover from one of the target copy storages110 a, 110 b to the target storage 104 b, such as, but not limited to,the IBM HyperSwap product which establishes failover sessions from theestablished copy pairs. (Geographically Dispersed Parallel Sysplex,GDPS, Tivoli, and HyperSwap are registered trademarks of IBM incountries throughout the world).

In alternative embodiments, the functionality described with respect tothe replication manager 116 and failover manager 126 may be implementedin a single storage manager program or in multiple different programmodules.

In one embodiment a first type of copy operation comprises the PiT copyoperation and a second type of copy operation comprises a mirror copyoperation. In additional embodiments, the first and second copyoperation subject to the operations may comprise other copy operationsknown in the art.

The network 112 may comprise a Storage Area Network (SAN), Local AreaNetwork (LAN), Intranet, the Internet, Wide Area Network (WAN),peer-to-peer network, wireless network, arbitrated loop network, etc.The storages 104 a, 104 b, 108 a, 108 b, 110 a, 110 b may each beimplemented in one or more storage devices, or an array of storagedevices configured as Just a Bunch of Disks (JBOD), Direct AccessStorage Device (DASD), Redundant Array of Independent Disks (RAID)array, virtualization device, tape storage, flash memory, etc. Thenstorage devices in which the storages 104 a, 104 b, 108 a, 108 b, 110 a,110 b are implemented may comprise hard disk drives, solid state storagedevice (SSD) comprised of solid state electronics, such as a EEPROM(Electrically Erasable Programmable Read-Only Memory), flash memory,flash disk, Random Access Memory (RAM) drive, storage-class memory(SCM), etc., magnetic storage disk, optical disk, tape, etc.

FIG. 2 illustrates an embodiment of an instance of a copy relationship200 _(i) e.g., copy relationships 200 ₁, 200 ₂, 200 ₃, and 200 ₄, whichmay be included in the copy relationships 200 and 200 a, as including acopy pair identifier (ID) 202; a primary storage 204 from which data iscopied; a secondary storage 206 to which data is mirrored; a use remotepoint-in-time (“PiT”) copy indicator 208 indicating whether a remote PiTcopy operation will be performed for the relationship or whether data isto be directly copied from the primary 204 to the secondary 206 storagesif remote PiT copy is not used; and a status 210 of the copyrelationship, such as pending (indicating that data is in the process ofbeing copied from the primary 204 to the secondary 206 storage, andduring a pending status, data is not synchronized), duplex (indicatingthat the pair is synchronized and all writes to the primary have beenapplied to the secondary), simplex (the relationship has not beenestablished), suspended (when the primary 204 cannot be successfullysynchronized to the secondary 206).

FIG. 3 illustrates an embodiment of a remote pair PiT copy establishrequest 300 that the host 100 would issue to the storage server 102 ahaving the source 104 a and target 104 b storages for which a remote PiTcopy operation can be performed. The request 300 includes a command code302 identifying the remote pair PiT copy establish request; a sourcestorage 304 that is the source of the PiT copy; a target secondarystorage 306 that is the target of the PiT copy; and a preferred orrequired setting 308. The required setting indicates that the request300 will fail if a remote PiT copy operation cannot be used for one ofthe pairs, or copy relationships, to allow a remote PiT copy from onesource copy storage 108 a, 108 b to one target copy storage 110 a, 110b. The required setting indicates the request 300 cannot tolerate thepairs all being in a duplex pending state where data is physicallycopied from the target storage 104 b to all of the target copy storages110 a, 110 b. A preferred setting indicates that the request 300 cantolerate all pairs going into a duplex pending state if the remote PiTcopy cannot be performed, requiring that a mirror copy operation isperformed to copy the target storage 104 b to the target copy storages110 a, 110 b.

FIG. 4 illustrates an embodiment of operations performed by thereplication manager 114 at the host 100 to establish the underlying copyrelationships 200 ₁, 200 ₂, 200 ₃, and 200 ₄ before processing theremote pair PiT copy establish request 300. These operations of FIG. 4may each be initiated in response to user entered establish commands viaa user interface of the replication manager 114 or automaticallyexecuted as part of a script program including the mirror copyrelationship establish commands. Upon initiating (at block 400) theoperations to establish mirror copy relationships 200 ₁, 200 ₂, 200 ₃,and 200 ₄, the replication manager 114 establishes (at block 402) amirror copy relationship 200 ₁ between the source storage 104 a and afirst source copy storage 108 a on different storage servers 102 a, 102b where the indicator 208 may be set to use or not use remote PiT copy.At block 404, the replication manager 114 establishes a mirror copyrelationship 200 ₂ between the source storage 104 a and the secondsource copy storage 108 b on different storage servers 102 a, 102 cwhere the indicator 208 may be set to use or not use remote PiT copy. Atblock 406, the replication manager 114 establishes a mirror copyrelationship 200 ₃ between the target storage 104 b and a first targetcopy storage 110 a on different storage servers 102 a, 102 b where theindicator 208 may be set to use or not use remote PiT copy. At block408, the replication manager 114 establishes a mirror copy relationship200 ₄ between the target storage 104 b and a second target copy storage110 b on different storage servers 102 a, 102 c where the indicator 208may be set to use or not use remote PiT copy.

Once the mirror copy relationships 200 ₁, 200 ₂, 200 ₃, and 200 ₄ areestablished, data is copied from the primary storage, e.g., source 104a, target 104 b storages, to a secondary storage, e.g., copy storages108 a, 108 b, 110 a, 110 b, to synchronize the data therebetwen. In oneimplementation, the user may set the indicator 208 so only one each ofthe source and target copy relationship pairs, e.g., 200 ₁, 200 ₃, usethe remote PiT copy and other of the source and target copyrelationships e.g., 200 ₂, 200 ₄, have the indicator 208 set to not usethe remote PiT copy, i.e., the relationship is placed in a duplexpending state until data is physically copied over. However, the usermay also indicate other settings for the indicator 208 in the copyrelationships.

In certain implementations, the replication manager 114 to may only beable to implement the remote pair PiT copy establish command 300 ifthere is no ambiguity as to which of the multiple secondary storages 108a, 108 b, 110 a, 110 b in the copy relationships, e.g., 200 ₁, 200 ₂,200 ₃, 200 ₄, will use a remote PiT copy operation and which ones willnot. This means in certain implementations, the remote PiT copyoperation cannot be performed if multiple of the source and targetrelationships each specify to use the remote PiT copy because in suchcase there is ambiguity as to which copy relationship should be used forthe remote PiT copy operation. Further, there may also be ambiguity ifthere are multiple relationships but none specify to use the remote PiTin the indicator 208. Yet further, if there is only one relationship,then there is no ambiguity regardless of the setting of use remote PiTindicator 208.

FIG. 5 illustrates an embodiment of operations performed by thereplication managers 114, 120 to process a remote pair PiT copyestablish command 300 to address the situation when there is ambiguityas to which copy relationship should be used for the remote PiT copyoperation. The replication manager 122 at the storage server 102 areceives (at block 500) from the replication manager 114 in the host 100a remote pair PiT copy establish command 300 for the source storage 104a to the target storage 104 b indicating required or preferred mirror308. This command 300 may be received after full duplex stateestablished between all the relationships 200 ₁, 200 ₂, 200 ₃, 200 ₄.The replication manager 200 performs (at block 502) a capability checkto determine whether there is ambiguity as to which source storage andtarget storage copy relationships 200 ₁, 200 ₂, 200 ₃, 200 ₄ indicate touse the remote first PiT copy operation. In one embodiment, ambiguity isdetermined if zero or more than one of the indicators 208 for each ofthe source and target copy relationships indicates to use the first typecopy operation. For instance, there is ambiguity if no source copyrelationship and/or no target copy relationship has the indicator 208set to indicate to use the remote PiT copy or if more than two of thesource copy relationships and/or more than two of the target copyrelationships have the indicator 208 set to indicate to use the remotePiT copy. In such implementations, there is no ambiguity if one sourcecopy relationship and one target copy relationship have the indicator308 set to indicate to use the remote PiT copy, because the secondaryvolumes of the mirror copy relationships to subject to the remote PiTcopy command are definite.

If (at block 504) the configuration is ambiguous and if (at block 506)the request 300 has the required setting 308, then the remote pair PiTcopy establish request 300 is failed (at block 508). Otherwise, if thesetting 308 is the preferred setting, then the replication manager 122performs (at block 510) a PiT copy between the source storage 104 a tothe target storage 104 b at the storage server 102 a. The replicationmanager 122 further establishes (at block 512) duplex pending state forthe target copy relationships 200 ₂, 200 ₃ to cause the physical copyingof data between the indicated primary (source storage) and secondarystorages (first and second source copy storages) in the target copyrelationships on the different storage servers 102 a, 102 b, 102 c. Whenthis occurs, the target storage subject to the pending state cannot beavailable for a failover operation until the copying completes and thestate is duplex.

If (at block 504) the configuration is not ambiguous, i.e., it is clearwhich source and target copy relationship to use for the remote PiTcopy, then the replication manager 122 performs (at block 514) a PiTcopy between the source storage 104 a to the target storage 104 b at thestorage server 102 a. For the source and target copy relationship havingthe use remote PiT copy indicator 308 set to use remote PiT copy, thereplication manager 122 sends (at block 516) the remote PiT copy commandto the storage server 102 b having the source copy storage 108 a, 108 bindicated as the secondary storage 206 in the source copy relationship200 ₁ or 200 ₂ and having the target copy storage 110 a, 110 n indicatedas the secondary storage 208 in the target copy relationship 200 ₃ or200 ₄. This remote PiT copy command causes the storage server 102 areceiving the command to perform a PiT copy from the source copy storageto the target copy storage, which are the secondary storages of copyrelationships whose primaries are subject to the PiT copy. For thetarget copy relationship not having the use remote PiT copy indicator208 set to use remote PiT copy, the replication manager 122 places (atblock 518) that target copy relationship, e.g., 200 ₃ or 200 ₄, in theduplex pending state until data is synchronized and can be returned tothe duplex state. From blocks 512 and 516, complete is returned (atblock 520) to the remote pair PIT copy establish request 300. For thesource copy relationship not having the use remote PiT copy indicator208 set to use remote PiT copy, writes to the primary storage 204(source storage 104 a) would be automatically synchronized to thesecondary storage 206 (source copy storages 108 a, 108 b).

In the described embodiments, the capability check is performed by thereplication manager 122 in the storage server 120 a receiving therequest 300. In an alternative embodiment, capability check and other ofthe operations of FIG. 5 may be performed by the replication manager 114in the host initiating the request 300.

The described embodiments provide techniques to process a remote pairPiT copy request in environments having multiple targets, or mirror copysecondary storages, to the source and target storages that are subjectto the remote pair PiT copy requests. Described embodiments include anindicator with the copy relationship indicating whether a remote PiTcopy command can be used with the secondary storage in the mirror copyrelationship so that a PiT copy operation can be performed from astorage in the same remote storage server that is also the secondarystorage of mirror copy relationship having as a primary storage thesource of the PiT request.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Java, Smalltalk, C++ or the like,and conventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

The computational components of FIG. 1, including the hosts 100 andstorage servers 102 a, 102 b, 102 c may be implemented in one or morecomputer systems, such as the computer system 602 shown in FIG. 6.Computer system/server 602 may be described in the general context ofcomputer system executable instructions, such as program modules, beingexecuted by a computer system. Generally, program modules may includeroutines, programs, objects, components, logic, data structures, and soon that perform particular tasks or implement particular abstract datatypes. Computer system/server 602 may be practiced in distributed cloudcomputing environments where tasks are performed by remote processingdevices that are linked through a communications network. In adistributed cloud computing environment, program modules may be locatedin both local and remote computer system storage media including memorystorage devices.

As shown in FIG. 6, the computer system/server 602 is shown in the formof a general-purpose computing device. The components of computersystem/server 602 may include, but are not limited to, one or moreprocessors or processing units 604, a system memory 606, and a bus 608that couples various system components including system memory 606 toprocessor 604. Bus 608 represents one or more of any of several types ofbus structures, including a memory bus or memory controller, aperipheral bus, an accelerated graphics port, and a processor or localbus using any of a variety of bus architectures. By way of example, andnot limitation, such architectures include Industry StandardArchitecture (ISA) bus, Micro Channel Architecture (MCA) bus, EnhancedISA (EISA) bus, Video Electronics Standards Association (VESA) localbus, and Peripheral Component Interconnects (PCI) bus.

Computer system/server 602 typically includes a variety of computersystem readable media. Such media may be any available media that isaccessible by computer system/server 602, and it includes both volatileand non-volatile media, removable and non-removable media.

System memory 606 can include computer system readable media in the formof volatile memory, such as random access memory (RAM) 610 and/or cachememory 612. Computer system/server 602 may further include otherremovable/non-removable, volatile/non-volatile computer system storagemedia. By way of example only, storage system 613 can be provided forreading from and writing to a non-removable, non-volatile magnetic media(not shown and typically called a “hard drive”). Although not shown, amagnetic disk drive for reading from and writing to a removable,non-volatile magnetic disk (e.g., a “floppy disk”), and an optical diskdrive for reading from or writing to a removable, non-volatile opticaldisk such as a CD-ROM, DVD-ROM or other optical media can be provided.In such instances, each can be connected to bus 608 by one or more datamedia interfaces. As will be further depicted and described below,memory 606 may include at least one program product having a set (e.g.,at least one) of program modules that are configured to carry out thefunctions of embodiments of the invention.

Program/utility 614, having a set (at least one) of program modules 616,may be stored in memory 606 by way of example, and not limitation, aswell as an operating system, one or more application programs, otherprogram modules, and program data. Each of the operating system, one ormore application programs, other program modules, and program data orsome combination thereof, may include an implementation of a networkingenvironment. The components of the computer 602 may be implemented asprogram modules 616 which generally carry out the functions and/ormethodologies of embodiments of the invention as described herein. Thesystems of FIG. 1 may be implemented in one or more computer systems602, where if they are implemented in multiple computer systems 602,then the computer systems may communicate over a network.

Computer system/server 602 may also communicate with one or moreexternal devices 618 such as a keyboard, a pointing device, a display620, etc.; one or more devices that enable a user to interact withcomputer system/server 602; and/or any devices (e.g., network card,modem, etc.) that enable computer system/server 602 to communicate withone or more other computing devices. Such communication can occur viaInput/Output (I/O) interfaces 622. Still yet, computer system/server 602can communicate with one or more networks such as a local area network(LAN), a general wide area network (WAN), and/or a public network (e.g.,the Internet) via network adapter 624. As depicted, network adapter 624communicates with the other components of computer system/server 602 viabus 608. It should be understood that although not shown, other hardwareand/or software components could be used in conjunction with computersystem/server 602. Examples, include, but are not limited to: microcode,device drivers, redundant processing units, external disk drive arrays,RAID systems, tape drives, and data archival storage systems, etc.

The terms “an embodiment”, “embodiment”, “embodiments”, “theembodiment”, “the embodiments”, “one or more embodiments”, “someembodiments”, and “one embodiment” mean “one or more (but not all)embodiments of the present invention(s)” unless expressly specifiedotherwise.

The terms “including”, “comprising”, “having” and variations thereofmean “including but not limited to”, unless expressly specifiedotherwise.

The enumerated listing of items does not imply that any or all of theitems are mutually exclusive, unless expressly specified otherwise.

The terms “a”, “an” and “the” mean “one or more”, unless expresslyspecified otherwise.

Devices that are in communication with each other need not be incontinuous communication with each other, unless expressly specifiedotherwise. In addition, devices that are in communication with eachother may communicate directly or indirectly through one or moreintermediaries.

A description of an embodiment with several components in communicationwith each other does not imply that all such components are required. Onthe contrary a variety of optional components are described toillustrate the wide variety of possible embodiments of the presentinvention.

When a single device or article is described herein, it will be readilyapparent that more than one device/article (whether or not theycooperate) may be used in place of a single device/article. Similarly,where more than one device or article is described herein (whether ornot they cooperate), it will be readily apparent that a singledevice/article may be used in place of the more than one device orarticle or a different number of devices/articles may be used instead ofthe shown number of devices or programs. The functionality and/or thefeatures of a device may be alternatively embodied by one or more otherdevices which are not explicitly described as having suchfunctionality/features. Thus, other embodiments of the present inventionneed not include the device itself.

The foregoing description of various embodiments of the invention hasbeen presented for the purposes of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseform disclosed. Many modifications and variations are possible in lightof the above teaching. It is intended that the scope of the invention belimited not by this detailed description, but rather by the claimsappended hereto. The above specification, examples and data provide acomplete description of the manufacture and use of the composition ofthe invention. Since many embodiments of the invention can be madewithout departing from the spirit and scope of the invention, theinvention resides in the claims herein after appended.

What is claimed is:
 1. A computer program product for copying data in astorage computing environment having a plurality of storage servers,wherein the computer program product comprises a computer readablestorage medium having program instructions embodied therewith, theprogram instructions executable by a processor to cause operations, theoperations comprising: establishing a source copy relationship to mirrordata from a source storage to a source copy storage; establishing atarget copy relationship to mirror data from a target storage to atarget copy storage; processing a first copy command to copy data fromthe source storage to the target storage in a first server; in responseto the first copy command: performing a first copy operation from thesource storage to the target storage; sending a second copy command to asecond server having the source copy storage to perform a second copyoperation from the source copy storage to the target copy storage in thesecond server; and placing the target copy relationship in a pendingstate until data is synchronized between the target storage and thetarget copy storage.
 2. The computer program product of claim 1, whereinthe first and the second copy operations comprise point-in-time copyoperations.
 3. The computer program product of claim 1, wherein thesource copy storage comprises a first source copy storage, wherein thetarget copy storage comprises a first target copy storage, wherein thesource copy relationship comprises a first source copy relationship, andwherein the target copy relationship comprises a first target copyrelationship, wherein the operations further comprise: establishing asecond source copy relationship to mirror data from the source storageto a second source copy storage; establishing a second target copyrelationship to mirror data from the target storage to a second targetcopy storage, wherein the first and the second source and target copyrelationships indicate whether to use a remote copy operation; anddetermining whether there is ambiguity as to which of the first and thesecond source and target copy relationships to use for the remote copyoperation, wherein operations performed in response to the first copycommand are performed in response to determining that there is noambiguity as to which of the first and the second source and target copyrelationships to use for the remote copy operation.
 4. The computerprogram product of claim 3, wherein the first and/or the second targetcopy relationship in the pending state cannot be available for afailover operation until data is synchronized through the first and thesecond target copy relationships.
 5. The computer program product ofclaim 3, wherein in response to determining that there is ambiguity:establishing a pending state for the first and the second target copyrelationships in a pending state until data is synchronized between thetarget storage and the first target copy storage and between the targetstorage and the second target copy storage, respectively.
 6. Thecomputer program product of claim 5, wherein the first copy commandindicates whether the remote copy operation is required, wherein theestablishing the pending state in response to determining that there isambiguity is performed in response to determining that the first copycommand does not indicate that the remote copy operation is required. 7.The computer program product of claim 6, wherein the operations furthercomprise: failing the first copy command in response to determining thatthere is ambiguity and that the first copy command indicates that theremote copy operation is required.
 8. A system for copying data in astorage computing environment having a plurality of storage servers,comprising: a processor; and a computer readable storage mediumincluding program instructions to perform operations, the operationscomprising: establishing a source copy relationship to mirror data froma source storage to a source copy storage; establishing a target copyrelationship to mirror data from a target storage to a target copystorage; processing a first copy command to copy data from the sourcestorage to the target storage in a first server; in response to thefirst copy command: performing a first copy operation from the sourcestorage to the target storage; and sending a second copy command to asecond server having the source copy storage to perform a second copyoperation from the source copy storage to first target copy storage inthe second server; and placing the target copy relationship in a pendingstate until data is synchronized between the target storage and thetarget copy storage.
 9. The system of claim 8, wherein the first and thesecond copy operations comprise point-in-time copy operations.
 10. Thesystem of claim 8, wherein the source copy storage comprises a firstsource copy storage, wherein the target copy storage comprises a firsttarget copy storage, wherein the source copy relationship comprises afirst source copy relationship, and wherein the target copy relationshipcomprises a first target copy relationship, wherein the operationsfurther comprise: establishing a second source copy relationship tominor data from the source storage to a second source copy storage;establishing a second target copy relationship to mirror data from thetarget storage to a second target copy storage, wherein the first andthe second source and target copy relationships indicate whether to usea remote copy operation; and determining whether there is ambiguity asto which of the first and the second source and target copyrelationships to use for the remote copy operation, wherein operationsperformed in response to the first copy command are performed inresponse to determining that there is no ambiguity as to which of thefirst and the second source and target copy relationships to use for theremote copy operation.
 11. The system of claim 10, wherein the firstand/or the second target copy relationship in the pending state cannotbe available for a failover operation until data is synchronized throughthe first and the second target copy relationships.
 12. The system ofclaim 10, wherein in response to determining that there is ambiguity:establishing a pending state for the first and the second target copyrelationships in a pending state until data is synchronized between thetarget storage and the first target copy storage and between the targetstorage and the second target copy storage, respectively.
 13. The systemof claim 12, wherein the first copy command indicates whether the remotecopy operation is required, wherein the establishing the pending statein response to determining that there is ambiguity is performed inresponse to determining that the first copy command does not indicatethat the remote copy operation is required.
 14. The system of claim 13,wherein the operations further comprise: failing the first copy commandin response to determining that there is ambiguity and that the firstcopy command indicates that the remote copy operation is required.
 15. Amethod for copying data in a storage computing environment having aplurality of storage servers, comprising: establishing a source copyrelationship to mirror data from a source storage to a source copystorage; establishing a target copy relationship to mirror data from atarget storage to a target copy storage; processing a first copy commandto copy data from the source storage to the target storage in a firstserver; in response to the first copy command: performing a first copyoperation from the source storage to the target storage; and sending asecond copy command to a second server having the source copy storage toperform a second copy operation from the source copy storage to thetarget copy storage in the second server; and placing the target copyrelationship in a pending state until data is synchronized between thetarget storage and the target copy storage.
 16. The method of claim 15,wherein the first and the second copy operations comprise point-in-timecopy operations.
 17. The method of claim 15, wherein the source copystorage comprises a first source copy storage, wherein the target copystorage comprises a first target copy storage, wherein the source copyrelationship comprises a first source copy relationship, and wherein thetarget copy relationship comprises a first target copy relationship,further comprising: establishing a second source copy relationship tominor data from the source storage to a second source copy storage;establishing a second target copy relationship to minor data from thetarget storage to a second target copy storage, wherein the first andthe second source and target copy relationships indicate whether to usea remote copy operation; and determining whether there is ambiguity asto which of the first and the second source and target copyrelationships to use for the remote copy operation, wherein operationsperformed in response to the first copy command are performed inresponse to determining that there is no ambiguity as to which of thefirst and the second source and target copy relationships to use for theremote copy operation.
 18. The method of claim 17, wherein the firstand/or the second target copy relationship in the pending state cannotbe available for a failover operation until data is synchronized throughthe first and the second target copy relationships.
 19. The method ofclaim 17, wherein in response to determining that there is ambiguity:establishing a pending state for the first and the second target copyrelationships in a pending state until data is synchronized between thetarget storage and the first target copy storage and between the targetstorage and the second target copy storage, respectively.
 20. The methodof claim 19, wherein the first copy command indicates whether the remotecopy operation is required, wherein the establishing the pending statein response to determining that there is ambiguity is performed inresponse to determining that the first copy command does not indicatethat the remote copy operation is required.
 21. The method of claim 20,wherein the operations further comprise: failing the first copy commandin response to determining that there is ambiguity and that the firstcopy command indicates that the remote copy operation is required.